Colored gold alloy



Patented May 27, 1941 COLORED GOLD ALLOY Ludwig Weiss,Frankfort-on-the-Main, Germany, assignor to Chemical Marketing CompanyInc., New York, N. Y., a corporation of New York No Drawing. ApplicationMay 1, 1940, Serial No. I 332,841. In Germany April 13, 1939 Claims.

My invention relates to the manufacture of a purple colored gold alloycontaining thorium besides aluminum and gold.

It is known that gold combines with aluminum and forms an intermetalliccomposition of the formula AuAlz with a bluish or purple, amethystlikecolor, containing 78.5 parts of gold and 21.5 parts of Al. This alloy,known as amethyst or blue gold" is not workable because of its hardness,brittleness and its liability of break- Other gold alloys contain,besides gold and aluminum according to the formula AuAlz, additionalquantities of aluminum or other soft metals such as silver, tin, zinc,cadmium, bismuth, thallium either alone or in combination in quantitieswhich facilitate the workability of the alloy without a harmfulinfluence to the color effect. The total amount of these additional softmetals should not exceed 40% of the alloy. With these additions of softmetals gold alloys of various shades are obtained, for instance, fromred over a purple shade to a violet color, 1. e. especially amethystcolored red alloys which are workable and suitable for the manufactureof jewels.

Now it .was found that the qualities of the goldaluminum alloys,especially those of the formula AuAlz may be considerably improved withrespect to the workability by adding thorium in suitable amounts.

These new alloys according to my invention may, for instance, alsocontain thorium in quantities up to about besides gold and aluminum. Ifa beautiful blue color is desired, the contents of thorium in the alloymust be kept below 7%. It is also possible to add very small amounts ofthorium, for instance, such which do not exceed 1%- of the whole alloy.Gold aluminum alloys with a thorium content of, for instance, 0.5% to 1%have a beautiful shade, good workability and' ductility. The thoriumcontent may even be kept lower, especially if other metals withimproving qualities are present. The lower limit of the content ofthorium is, for instance, about 0.5% of the total alloy.

Furthermore, I have found that the ductility of the alloys may beincreased by adding tin in quantities of about 7% besides gold, aluminumand thorium.

Generally, it has proved advantageous to keep Gold Aluminum 24,25Thorium 0.25 Tin 0.5

has a beautiful bluish color, good workability and may easily behallmarked.

In carrying out my invention I may proceed as follows: The compositionAuAlz, i. e. 78.5 parts of gold and 21.5 parts of aluminum, may serve asstarting material, whereby one or both of these metals are partlysubstituted by thorium or thorium and tin.

It has proved advantageous to substitute one part of the aluminum bythorium or thorium and tin respectively. This makes it possible toobtain beautiful workable alloys with a high content of gold, forinstance, 75% gold, corresponding to a hallmark of 18 karat.

The alloys, according to my invention, may als contain, besides the mainconstituents gold, aluminum and thorium or thorium and tin, smallquantities of other metals such as silver, zinc,

cadmium and the like.

Other components of the alloy may be iron, nickel, cobalt, manganese,copper. The addition of small quantities of these metals either alone orin combination may influence the qualities of the alloys with respect toductility and the like and'also in regard to the color shade. Of course,the quantity of these additional metals is proportioned in such mannerthat harmful influences may not occur. Generally, it was foundadvantageous to keep the amount of these metallic additions, alone orcombined with each other, below 5% preferably below 2% of the totalalloy. As the alloys are susceptible against oxygen, I prefer to workairsealed. For instance, I may proceed in such manner that at first thealuminum is molten under a salt layer whereupon the other ingredientsare added in the following order: tin, gold, thorium.

Thealloys may be used for various purposes. They are especially suitedfor the manufacture of jewels.

What I claim is:

21.5% aluminum, and from about 0.5% to 10% thorium.

3. A workable gold alloy having a purple colored shade consisting offrom about 71.5% to about 78.5% of gold, from about 14.5% to about 21.5%of aluminum, and from about 0.5% to about 7% or thorium.

4. A workable gold alloy having a purple oolored shade consisting offrom about 75.5% to 78.5% of gold, from about 18.5% to about 21.5% ofaluminum, and about,3% of thorium.

5. A workable gold alloy having a purple colored shade consisting offrom about'68.5% to about 78.5% gold, from about 0.5% to about 10%thorium, and the remainder substantially all aluminum, the aluminumconstituting not over 10 24.25% of the alloy.

LUDWIG wmss.

